Is there any limit to the amount of tiles that can be added / palettes that can be used? I know by default, there's only so much room in the tileset and there also appears to be a limit in the number of palettes. I could see this becoming a problem if someone wanted to add a lot of custom tiles.
depending on which rom base you use, you can only use up to 12 palettes per tileset (which includes the main tileset you will use which is Tileset 0). So in reality, for example in EM, you only have palettes 6-12 I believe to manipulate every new tileset you make. So you have to make them work but thats not hard. I usually group gray/dark/white tiles together, blue tiles together, etc... It isn't really a problem but yes you are restricted to the amount of tiles per tileset.
I think I did, let me try again. I'll see if it works. I'll come back and edit this post.
Edit: I tried, it still changed it. Do you think I can just edit the converted picture in paint? Or would that mess it up?
So the background color really doesnt matter too much. Save the palette and go into advancemap. Insert the palette and if the bg color is still the gray color, just figure out what the rgb values are for the green bg color or whatever you used and change the offsets of the bg color for that palette to match that of your image and save the palette info in amap then save tileset 2 and open your tileset image in mspaint and drag n drop and it should work